Alternate Precipitation Methods for Gold

[Kreis412]

I apologize if this is a repeat thread but i couldn't find it. I was wondering about different chemicals or substances i could use to drop gold and why they'd be good or bad. Such as ive seen you can use ferrous sulfide so why not ferrous oxide. I don't know maybe it seems dumb but i find it interesting. Or maybe someone here has a book or PDF with all the different methods. I guess specifically I'm interested in the ferrous sulfide and also zinc. I've even heard sugar can be used.
Well thanks, and if it's a bad thread just delete it. I get there's probably more important things to do.
Nah just kidding i wont be sad lol

 

[Yggdrasil]

I apologize if this is a repeat thread but i couldn't find it. I was wondering about different chemicals or substances i could use to drop gold and why they'd be good or bad. Such as ive seen you can use ferrous sulfide so why not ferrous oxide. I don't know maybe it seems dumb but i find it interesting. Or maybe someone here has a book or PDF with all the different methods. I guess specifically I'm interested in the ferrous sulfide and also zinc. I've even heard sugar can be used.
Well thanks, and if it's a bad thread just delete it. I get there's probably more important things to do.
Nah just kidding i wont be sad lol

I doubd Ferrous Oxide works since it is basically “rust” and Zinc is cementing but it is not selective.
You have SMB which is basically SO2, Ascorbic Acid and Oxalic acid and so on. It is all in here.
If you want to cement it out better use Copper since it is “selective” for PMs

But use the search function it is all in here.

 

[FrugalRefiner]

I apologize if this is a repeat thread but i couldn't find it. I was wondering about different chemicals or substances i could use to drop gold and why they'd be good or bad. Such as ive seen you can use ferrous sulfide so why not ferrous oxide.

I've never heard of using ferrous sulfide. Ferrous sulfate works. Tiny differences in chemical names can make all the difference.

Dave

 

[Yggdrasil]

I've never heard of using ferrous sulfide. Ferrous sulfate works. Tiny differences in chemical names can make all the difference.

Dave

That one slipped my eye.

 

[orvi]

Hydrazine
Oxalic acid
Ascorbic acid = Vitamin C
Sodium nitrite
Hydroquinone
Sodium and potassium sulfites, metabisulfites, hydrogensulfites etc. (all work effectively)
Sucrose (used by Krastsvetmet russian refinery, they just claim it, never tried myself)
Ferrous sulfate
SO2 gas - for me, the best choice in terms of price, use and produced Au quality

FeO is not very soluble, hard to say how it will show up in real life. If it is some hydrated oxide form (which I doubt is easily available commercially), maybe. But it will consume acid upon addition, so I won´t be very excited about it´s practical use.

List of less selective reducing agents with good selectivity over base metals - often precipitate all PMs included :
Copper (copper cementation of gold works pretty nicely, precipitate fall off the copper surface pretty nicely, but it reduce whatever PMs you have in solution)
Formic acid/formate - also, all PMs will drop alongside gold.
Stannous chloride - bad for precipitations (best for testing), but it does reduce gold. Not recommended.

Stripping agents used for SX of gold from solutions:
Diethyl ether - low end, very hazardous due to insane flammability, but works
Butyl diglyme
Methyl isobutyl ketone (MIBK)
These usually require special conditions to achieve good results, but can be extraordinarily selective. Subsequent stripping is needed, followed by precipitation (or combined "precipitation stripping" is applied). Flammable, forming peroxides, sometimes cumbersome to handle. Require extraction apparatus to proceed.

Complexing agents for gold:
Pyridine.HBr can precipitate gold from organic liquids, but only to some extent.
Ethylenediamine (N,N´-dimethyl) bis-benzamide - very effective relatively selective precipitant for gold, recent advance, precipitate gold complex, which is subsequently filtered, stripped, and precipitant reused.
SuperLig products - very expensive molecular recognition complexing agents, supported on solid phase. Highest end of current technology. Virtually exclusive selectivity towards the target element (they produce selective resins for individual PGMs, Au and also for barrens toxic elements removal such as Hg)

 

[Kreis412]

I apologize if this is a repeat thread but i couldn't find it. I was wondering about different chemicals or substances i could use to drop gold and why they'd be good or bad. Such as ive seen you can use ferrous sulfide so why not ferrous oxide. I don't know maybe it seems dumb but i find it interesting. Or maybe someone here has a book or PDF with all the different methods. I guess specifically I'm interested in the ferrous sulfide and also zinc. I've even heard sugar can be used.
Well thanks, and if it's a bad thread just delete it. I get there's probably more important things to do.
Nah just kidding i wont be sad lol

Oh and even more speci

Hydrazine
Oxalic acid
Ascorbic acid = Vitamin C
Sodium nitrite
Hydroquinone
Sodium and potassium sulfites, metabisulfites, hydrogensulfites etc. (all work effectively)
Sucrose (used by Krastsvetmet russian refinery, they just claim it, never tried myself)
Ferrous sulfate
SO2 gas - for me, the best choice in terms of price, use and produced Au quality

FeO is not very soluble, hard to say how it will show up in real life. If it is some hydrated oxide form (which I doubt is easily available commercially), maybe. But it will consume acid upon addition, so I won´t be very excited about it´s practical use.

List of less selective reducing agents with good selectivity over base metals - often precipitate all PMs included :
Copper (copper cementation of gold works pretty nicely, precipitate fall off the copper surface pretty nicely, but it reduce whatever PMs you have in solution)
Formic acid/formate - also, all PMs will drop alongside gold.
Stannous chloride - bad for precipitations (best for testing), but it does reduce gold. Not recommended.

Stripping agents used for SX of gold from solutions:
Diethyl ether - low end, very hazardous due to insane flammability, but works
Butyl diglyme
Methyl isobutyl ketone (MIBK)
These usually require special conditions to achieve good results, but can be extraordinarily selective. Subsequent stripping is needed, followed by precipitation (or combined "precipitation stripping" is applied). Flammable, forming peroxides, sometimes cumbersome to handle. Require extraction apparatus to proceed.

Complexing agents for gold:
Pyridine.HBr can precipitate gold from organic liquids, but only to some extent.
Ethylenediamine (N,N´-dimethyl) bis-benzamide - very effective relatively selective precipitant for gold, recent advance, precipitate gold complex, which is subsequently filtered, stripped, and precipitant reused.
SuperLig products - very expensive molecular recognition complexing agents, supported on solid phase. Highest end of current technology. Virtually exclusive selectivity towards the target element (they produce selective resins for individual PGMs, Au and also for barrens toxic elements removal such as Hg)

Thank you, i didnt think sodium nitrate would work. Isn't that salt peter? Anyway, thank you i really appreciate the help.

 

[Kreis412]

I just used the search bar as i was told to, and i saw vitamin C works. Wouldn't that make it more acidic? Or is it to kill the nitric acid?

 

[Kreis412]

I just used the search bar as i was told to, and i saw vitamin C works. Wouldn't that make it more acidic? Or is it to kill the nitric acid?

Actually i found how bit is it gold specific?

 

[Shark]

Yes that is vitamin C. It is pretty specific for gold. Better than some more common precipitants.

It is sodium nitrite (to drop gold) not sodium nitrate ( to make poormans AR).

 

[FrugalRefiner]

It is sodium nitrite (to drop gold) not sodium nitrate ( to make poormans AR).

Indeed! As I pointed out earlier, you must be very careful with chemical names. A single letter can mean the difference between success and catastrophe.

Dave

 

[Kreis412]

Yes that is vitamin C. It is pretty specific for gold. Better than some more common precipitants.

It is sodium nitrite (to drop gold) not sodium nitrate ( to make poormans AR).

Man those ates and ites always screw me up

 

[grainsofgold]

I've not tried using Sodium Nitrite ( not Sodium Nitrate) to drop gold from AR solution but I've hears it works well and has a benefit that if the AuCl has a little free nitric in solution it still works -

If anyone has used this method I would appreciate your posting on the process please -

Sodium Nitrite is used in the food industry but not easily available here in the US due to it being known as a suicide chemical used by young adults- We have an account with a chemical company so we can get it -

Does Sodium Nitrite have a shelf life? What's the best way to store it for it to last and how long will it last stored ?.

Thanks

GOG

 

[jord]

I've not tried using Sodium Nitrite ( not Sodium Nitrate) to drop gold from AR solution but I've hears it works well and has a benefit that if the AuCl has a little free nitric in solution it still works -

If anyone has used this method I would appreciate your posting on the process please -

Sodium Nitrite is used in the food industry but not easily available here in the US due to it being known as a suicide chemical used by young adults- We have an account with a chemical company so we can get it -

Does Sodium Nitrite have a shelf life? What's the best way to store it for it to last and how long will it last stored ?.

Thanks

GOG

Same here in the UK you cannot just buy it most places you have to fill out a declaration of use.

I have used sodium nitrite a few times, I used it as a second precipate on AR solutions from carat scrap jewellery. It did produce clean drops but not sure if you can just use SMB and ascorbic acid both are much easier to source and if you are into you're chemistry may I suggest a s02 bubbler.

Be careful when using add in small increments as it fizzes up and cause the solution to run out of the beaker. It will also give off the red fumes which if you cover the beaker whilst fuming I believe the fumes can go back into the solution and cause gold to redigest. In my experience anyways I could be wrong somebody more experienced may be able to chime in.

The shelf life on the bottle says 12 months, not tried it after that it may still work if it has been stored well sealed.

Either way it's another tool in the belt but other methods can achieve same results.

 

[4metals]

I believe the fumes can go back into the solution and cause gold to redigest.

It's not so much fumes going back into solution as it is free nitric existing before you started dropping the gold. If the gold was totally dissolved and the reaction stopped, it will not blow red fumes because there is nothing to dissolve to complete the reaction. As you start dropping gold you may see red fumes evolve and that is because the remaining free nitric in solution is re-dissolving what you drop. This will continue until all of the free nitric is used up and then the gold will drop and stay dropped.

I prefer a cylinder of SO₂ to drop the gold. The same thing happens there, gold drops and excess free nitric re-dissolves it. I think the SO₂ will make the cleanest drop.